JP, P2004-288949A discloses a semiconductor device including a semiconductor element and a package housing this semiconductor element. The package includes a base board, a peripheral wall provided on the top surface of the base board so as to surround a semiconductor element, and a lid provided on the upper side of the peripheral wall. The base board, the peripheral wall and the lid together form a space where a semiconductor element is housed (hereinafter, also referred to as “semiconductor element housing space”). In this semiconductor element housing space, the semiconductor element and an internal substrate with a matching circuit mounted thereon are fixed on the top surface of the base board. Two cut-away portions are provided in the peripheral wall of the package. Feed-through terminals to connect the internal substrate to peripheral electronic parts provided outside the package are fixed to the cut-away portions of the peripheral wall. The feed-through terminals and the internal substrate are connected to each other by wires formed by wire bonding or other methods. The internal substrate and the semiconductor element are also connected to each other by a wire formed by wiring bonding or other methods.
In recent years, to meet the demand for smaller and lighter-weight semiconductor devices, semiconductor element housing packages have been desired to have a smaller dimension in the thickness direction thereof. On the other hand, the dimension of each feed-through terminal in the thickness direction sometimes increases because the voltage and the frequency used by the semiconductor device serve as constraints on the size and the insulation resistance of the feed-through terminal. In these circumstances, thinning of the semiconductor element housing package described in JP, P2004-288949A is difficult due to the large dimension of the feed-through terminal in the thickness direction.
In addition, semiconductor devices tend to contain thinner semiconductor elements and thinner internal substrates. Accordingly, if feed-through terminals of the semiconductor element housing package described in JP, P2004-288949A have a large dimension in the thickness direction thereof, there is a level difference between the position where the wire connecting the corresponding feed-through terminal to the internal substrate is connected to the feed-through terminal and the position where the wire is connected to the internal substrate. The level difference elongates the wire connecting the internal substrate to the feed-through terminal and thus generates undesirable inductance (L). The inductance (L) causes mismatching of impedances between the internal substrate and the feed-through terminal, and thus impairs electrical characteristics, such as the output and the efficiency, of the semiconductor device.